Silver halide emulsion containing pyrrolidine proline or hydroxyproline sensitizers



United States Patent 01 hoe 3,514,292 Patented May 26, 1970 3,514,292 SILVER HALIDE EMULSION CONTAINING PYR- ROLIDINE PROLINE OR HYDROXYPROLINE SENSITIZERS Raymond Joseph Le Strange, Middletown, N.J., asslgnor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed May 19, 1967, Ser. No. 639,655

Int. Cl. G03c 1/28 US. Cl. 96107 7 Claims ABSTRACT OF THE DISCLOSURE A gelatino silver halide emulsion of increased sensitivity to radiation is obtained by adding a sensitizing amount of pyrrolidine, 2-pyrrolidine carboxylic acid (proline), or 4- hydroxy-2-pyrrolidine carboxylic acid hydroxyproline).

arable constituents, ranging from higher molecu ar weight polypeptide combinations of amino acids to lower molecular weight polypeptide fragments, and may even contain carbohydrates, aldehydes and other organic acids which sensitometrically affect photographic emulsions.

Experimental data has been reported where various individual proteins, such as tyrosine, alanine, proline, hydroxyproline, leucine, cystine and others were added to ammoniacal, positive, silver bromide emulsions, and the sensitometric effects were observed. The proteins were added in an amount proportional to their concentration in gelatin. The results reported that while proline and hydroxyproline retard the appearance of fog in the developed emulsion, they reduce the speed of the emulsion.

Recent trends toward improved processing characteristics, such as shorter drying times and lower residual thiosulfate content, have resulted in reducing the amount of binder, e.g. gelatin, contained in the emulsion. This reduction in binder content in many instances is accompanied by a significant loss in sensitivity.

This invention relates to a improved gelatino silver halide emulsion wherein pyrrolidine, 2-pyrrolidine carboxylic acid, or 4-hydroxy-2-pyrrolidine carboxylic acid is added, in the amount of from 0.13 to 3.34 grams per mole of silver, to increase sensitivity to radiation without increasing fog.

The addition of these compounds in their pure form allows for controlled use and reproducible sensitization. In addition, the compounds of this invention provide the advantages of gelatin-type sensitization, without the undesirable processing characteristics of the binder itself.

In general the invention comprises a conventionally made emulsion to which has been added a small amount of pyrrolidine, 2-pyrrolidine carboxylic acid (proline), or 4hydroxy-2-pyrrolidine carboxylic acid (hydroxyproline) to improve its sensitivity to radiation without increasing its fog level. The emulsion may be one of various gelatino-silver halide emulsions and may include those having lower gelatin binder content. The sensitizing agents of this invention should be added in amounts from 0.05 to 5.0 grams per 1.5 mole of silver.

In the preferred process of the invention the pyrrolidine,

Sample N 0.

proline, or hydroxyproline is added to the emulsion after digestion and before coating, although it may be added any time after the emulsion is coagulated, washed, and redispersed. The preferred emulsion product of this invention contains from 0.20 to 0.40 gram per 1.5 mole of silver of the pyrrolidine, proline, or hydroxyproline and also contains a reduced amount of gelatin of about grams to 130 grams per 1.5 mole of silver. This will give a photographic element which has a lower binder content and can be processed faster after exposure without a substantial loss in photographic sensitivity. The preferred silver halide is silver bromoiodide.

Several preferred embodiments of the present invention are illustrated by the following examples.

EXAMPLE 1 through an aluminum /'2 stepwedge and no screen, for one minute at 200 kilovolts potential and 4 milliamps current. The samples were exposed, processed, and read as in Example 2, except that the relative speeds were measured at a density of 1.5. The following table shows the sample compositions and the resulting relative speed, average gradient, and net fog levels.

Relative Speed Average Gradient Net Fog EXAMPLE 2 A gelatino silver bromoiodide, X-ray emulsion, containing 98.2 mole percent of AgBr and 1.8 mole percent of AgI, was coagulated, washed, and redispersed by the method described in assignees patent to J. A. Moede, US. 2,772,165. The redispersed emulsion, comprising approximately grams of gelatin per 1.5 mole of silver, was sensitized with gold and sulfur compounds in the conventional manner. After digestion, the emulsion was cooled and dextran added as described in assignees patent to A. B. Jennings, U .8. 3,063,838. Stabilizers and coating aids, such as saponin, were also added to the emulsion. The emulsion was then divided into two equal parts. To the first part was added 0.32 g./l.5 moles of Ag of 2- pyrrolidine carboxylic acid; to the second part nothing was added.

Two samples, coated on one side, were exposed to X-ray radiation through a medium speed fluorescent medical X-ray screen and an aluminum /2 stepwedge for second at 70 kilovolts potential and 2 milliamps current. Each sample was developed, fixed, washed, and dried in the conventional manner. In order to simulate double sided coating, each sample was cut longitudinally through the stepwedge exposed area, and the halves of the sample were placed, base sides in contact with each other with steps of equal density matched, in a conventional densitometer. The relative speeds of the two samples were measured at a density of 1.0 and the net fog reading was obtained by subtracting base density from the readings.

The sample with the 2-pyrrolidine carboxylic acid added exhibited higher relative speed, 197, and no increase in net fog level, 0.16, when compared to the control sample with no 2-pyrrolidine carboxylic acid added (speed, 153; net fog, 0.16).

EXAMPLE 3 each containing 1.5 moles of silver halide and 100 grams of gelatin. A dilferent amount of proline was added to each portion.

Single coated samples of each emulsion were prepared by methods well known in the coating art, and each sample was exposed through a /2 stepwedge to a xenon flash of 10 seconds duration at a distance of 6% inches, developed in a high energy developer, fixed, washed, and dried by conventional methods. The relative speed of each sample was measured at a density of 3.5 b conventional methods on a standard densitometer, as was the average gradient and net fog. The compositions and sensitometric results are shown in the table below:

Sample Compound Amount (gJ Relative Average 0. dded 1.5 moles of Ag) Speed Gradient Net Fog 1 Control 153 2.37 0.16 0. 180 2.80 0. 16 0. 10 190 2. 63 0.15 0. 19s 2. 57 0. 18 0.08 173 2. 0.16 0. 16 183 2. 66 0. 1s 0. 32 197 2. 68 0. 16 0. 09 160 2. 46 0. 14 0. 18 170 2. 7e 0. 14 0.36 180 2. 64 0.16

EXAMPLE 4 Amount of emul1on w P p 1n lq F P that Sample Proline (g./1.5 Relative Average prior to digestlon the emulsion was d1v1ded into two moles of p d Gradwnt Net Fog parts, one part having proline added to it prior to digestion 0 l 100 ()0 a; and one part continuing through the digestion step with- 8-38 i8 out proline. After digestion, the emulsion containing no proline was divided into two parts, a control and a portion to which proline was added. Coated samples were exposed, processed and analyzed as in Example 2. The compositions and results are shown in the table below.

Amount of Praline (g./1.5 mole Ag) Sample Before Aft-er Relative Average N0. Digestion Digestion Speed Gradeint Net Fog EXAMPLE 5 An emulsion was prepared as in Example 2, except that just after digestion and prior to the addition of final adjuvants, the emulsion was divided into six parts and a diflFerent amount of proline was added to each part. The compostions and sensitornetric data are shown in the table below, the coated samples being exposed and processed as in Example 2.

A gelatino silver bromochloride emulsion, containing 80.0 mole percent of AgBr and 20.0 mole percent of silver chloride, was coagulated, washed, and redispersed by the method described in assignees patent to J. A. Moede, US. 2,772,165. The redispersed emulsion, containing bulking gelatin and gold and sulfur sensitizers was digested at 136 F. for minutes. After digestion, stabilizers and coating aids, such as saponin were added, and H the resulting emulsion was divided into three portions,

The speed of the control was assigned the value 100.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A gelatino-silver halide photographic emulsion containing from about 0.05 to 5.0 grams per 1.5 mole of silver a sensitizer ofpyrrolidine, 2-pyrrolidine carboxylic acid or 4-hydroxy-2-pyrrolidine carboxylic acid.

2. An improved emulsion as defined in claim 1 where said emulsion contains about to grams of gelatin per 1.5 mole of silver.

3. An improved emulsion as defined in claim 2 where said sensitizer is present in an amount of about 0.20 to 0.40 gram per 1.5 mole of silver- 4. A gelatino-silver halide photographic element having a gelatino-silver halide emulsion layer containing from about 0.05 to 5.0 grams per 1.5 mole of silver a sensitizer of pyrrolidine, 2-pyrrolidine carboxylic acid or 4-hydroxy- 2-pyrrolidine carboxylic acid.

5. An improved photographic element as defined in claim 4 where said element contains about 80 to 130 grams of gelatin per 1.5 mole of silver.

6. An improved element as defined in claim 5 where said sensitizer is present in an amount of about 0.20 to 0.40 gram per 1.5 mole of silver.

7. In a process for preparing a gelatino silver halide the improvement which comprises adding to said emulsion from about 0.05 to 5.0 grams per 1.5 mole of silver a sensitizer of pyrrolidine, 2-pyrrolidine carboxylic acid or 4-hydroxy-2-pyrrolidine carboxylic acid.

References Cited UNITED STATES PATENTS 1/1955 Mueller 96107 4/ 1956 Warren 96-107 

